We can draw this figure out by using a '-' for a mile of the trail, and a 'l' for a sign. There will not be a sign at the beginning, but there will be a sign at the end. So let's draw that:
-l-l-l-l-l-l-l-l-l-l-l-l-l-l-l-l
By counting the amount of 'l's in the figure above, we are then able to determine that there will be 16 signs posted.
The sum of two irrational numbers, in some cases, will be irrational. However, if the irrational parts of the numbers have a zero sum (cancel each other out), the sum will be rational.
